In modern vehicles, safety-relevant vehicle systems, in particular, are continuously monitored for their reliability performance. Thus, for example, in the case of an electrically actuated brake system (brake-by-wire brake system), the path of a brake piston and the related brake pressure profile are monitored. If one of the above-mentioned operating parameters is outside an admissible value range or the relationship between the two operating parameters is no longer plausible, an error message is generated and the error may be displayed acoustically or visually. Monitoring is usually performed with the aid of a sensor system and of software which is stored in a control unit.
In the event of maintenance work on the vehicle, for example, on a brake system, operating states of individual components often occur which are outside a standard range and are therefore classified as errors by the monitoring unit. Thus, for example, after a brake lining change, the brake pistons are typically pushed back very far into the brake caliper, so that when the service brakes are actuated, the braking force builds up on the wheel brakes only with a great delay. This is detected as an error by the monitoring unit. However, this is not desirable in the case of maintenance work.
To avoid such error messages during or after the maintenance work, specially adapted diagnostic routines were therefore introduced, which support the maintenance work and should prevent an undesirable response of the monitoring units. However, these diagnostic routines are often not available to small, independent repair shops or do-it-yourself mechanics. In this case, performance of the maintenance work often results in a response of the monitoring unit.
When certain maintenance work is performed other approaches provide for automatic routines which support the repair-shop personnel when performing the maintenance work and are supposed to prevent the system monitoring from responding. Thus, for example, it may be provided that the brake pistons automatically move into a front position after a brake lining change. However, undesired activation of these automatic routines during normal operation may be safety-critical. Therefore, the automatic routines must be activated by the repair-shop personnel on the basis of a precisely defined sequence plan. This is, however, relatively complicated for the repair-shop personnel, so that the supporting routines are often not used.